In recent years there has been a very rapidly growing use of forcibly pumping blood or various feeding solutions into the veins of a patient by means of positively operated pumping devices. Such devices are much more accurate in the delivery of liquid to the patient than the older feeding by gravity only. Often, the intravenous feeding requires the delivery of very small amounts from 0.5 milliliters per hour up to as much as 500 to 1500 milliliters per hour (the equivalent of about 16 and 48 ounces, respectively, per hour). At the lower rates of feed there is frequent clogging of the delivery tube or needle which delivers the material into the veins of the patient and there is also considerable inaccuracy in the amount delivered over a period of time. This requires frequent checking of the gravity feed of such liquid to a patient by a nurse, or other qualified person. The present invention relates to an actuating device for a pump whereby the number of strokes in a given unit of time, such as one minute, and the length of the stroke (which is equivalent to saying the amount of fluid per stroke) is variable over a wide range. In this respect, the present invention comprises a big improvement over the pump actuator shown in my prior patent, U.S. Pat. No. 3,798,892, issued Mar. 26, 1974, as it is not only much smaller and therefore more easily portable, but is also more readily adjusted by the nurse or doctor in charge of administering the fluid to the patient. It is obvious that such a driver, or actuator, must be positive in its operation and must be readily adjustable to provide a wide range of delivery. The device of the present invention is more practical than that of my former patent in that it relieves the nurse or doctor on the floor from having to readjust the actuator each time it is used. It is a growing development in the field of medicine, particularly in the better hospitals, to prepare the material to be delivered in the hospital pharmacy and deliver it properly measured and marked with proper operating instructions to the floor where the patient is located so that the nurse does not have to take time to do a lot of figuring or adjusting of equipment. Such devices are disclosed in my copending applications, Ser. No. 514,219, for Measured Volume Drug Administration Device, filed Oct. 11, 1974, now U.S. Pat. No. 3,965,897, or Ser. No. 538,372, entitled Drug Dispenser for Use With Intravenous Feeding Pump, filed Jan. 3, 1975, now U.S. Pat. No. 3,976,068. In such hospitals, using the present invention, the pharmacy would also send to the nurses' station the proper cam to be used for the pump actuator so that the doctor or nurse would not be required to determine which cam should be used and what the length of stroke of the pump actuating cam follower should be.
As indicated above, the device of the present invention includes a set of cams which are easily removable from, or inserted into, the pump actuator. Thus, an operator has merely to set the material to be fed, the necessary tubing, sterilized pump, the proper cam (all of which can be furnished by the hospital pharmacy) into the pump actuator already at the bedside, insert the needle into the patient and initiate operation of the pump actuator. All of this is done without the operator (who is often very busy) having to bother about determining the number of strokes per minute, the length of each stroke, or otherwise setting the device.